The present invention relates to a failure diagnostic technique for conducting diagnosis on a failure in a solar battery module in a photovoltaic power generation system having a large number of solar battery modules.
In a large scale photovoltaic power generation system represented by a mega solar, several thousands to several tens of thousands of 100 to 200 w class solar battery modules are arranged in one power generation site.
In the respective solar battery modules, the output with the same solar radiation amount and on the same temperature condition is gradually reduced due to aged deterioration. In some of the modules, the output is radically reduced due to the quality in manufacturing or physical damage. The state of radically-reduced output is referred to as a failure.
As a method for detecting a failure in a solar battery module, a visual inspection, a heat generation inspection with a thermometer, and an inspection of electric characteristics using a tester are performed. These inspections are performed on each solar battery module. When the number of solar battery modules is increased, the labor and cost required for the inspections are increased.
Regarding this problem, Japanese Published Unexamined Patent Application No. 2010-123880 discloses a method for automatic failure determination of providing a measuring unit and a communication unit by solar battery module, and determining whether or not a failure has occurred in a solar battery by comparing a measurement result transmitted from the communication unit with a threshold value. Further, Japanese Published Unexamined Patent Applications Nos. 2005-340464 and 2011-181614 disclose a method of connecting a measuring unit by a unit of serially-connected solar battery modules, referred to as a string, for the sake of reduction of cost of the measuring unit, for failure determination. Further, from the viewpoint of improvement of inspection accuracy, Japanese Published Unexamined Patent Application No, 2011-216811 discloses a method of using a logical power generation amount calculated based on a solar radiation amount measured with an actinometer.